Drive transmitting connection



Nov; 24, 1970 G- A. KENDALL DRIVE TRANSMITTING CONNECTION Filed NOV. 27,1968 7'ii I3'i56' COUNTER CLOCKWlSE CLOCKWISE TORQUE LB-FT X IOO TORQUEC/ezz 1325]! (Mil n55 I ATTORNEY United States Patent 3,541,810 DRIVETRANSMITTING CONNECTION Glen A. Kendall, Dearborn, Mich, assignor toGeneral Motors Corporation, Detroit, Mich., a corporation of DelawareFiled Nov. 27, 1968, Ser. No. 779,479 Int. Cl. Flod 3/58, 7/00 US. Cl.64-28 9 Claims ABSTRACT OF THE DISCLOSURE There is a drive connectiondisposed between a rotatable input and a member driven by the input,which includes inner and outer metallic cylindrical sleeves having acompressed elastomeric, torque-transmitting sleeve therebetween. Thesleeves have aligned radial holes formed therein to accommodate steelballs which are effective on torque overload to provide driving contactbetween the inner and outer sleeves thereby limiting elastomeric sleeveslip and wear.

This invention relates to drive transmitting connections and moreparticularly to a torque transmitting coupling having an elastomerictorque transmitting device drivingly connecting torque-imparting andtorquereceiving members and having rigid torque-transmittingconstruction, operable in response to overload of the elastomericdevice, to transmit torque from one member to the other.

Elastomeric isolators are frequently utilized in the mechanical powertransmission field to operatively connect drive and driven members tosmooth out the flow of power therebetween. For example, such a yieldabletorque-transmitting connection may be used between the crankshaft of aninternal combustion engine and a beltdrive pulley which drives a fan orother accessory to effectively smother out engine-excited torsionalvibrations to provide for smoother operation of the driven accessory.

These elastomeric devices have proven to be highly effective andefficient in such drives; however, in some cases the elastomeric devicewill slip when excessive torque is applied between the drive and drivenmember. Such slippage causes the elastomeric device to Wear, thusimpairing its efiiciency and service life.

In this invention the slippage of the elastomeric device issubstantially eliminated by the provision of improved overload stopswhich rigidly connect the drive and driven member when an overloadcondition occurs. In a preferred form of the invention steel balls areutilized between inner and outer metal sleeves to provide ametalto-metal solid drive to prevent slippage of an elastomerictorque-transmitting sleeve compressed between the inner and outersleeves when the sleeve is overloaded or subjected to excessive shearstresses. The balls and metal sleeves are hardened with the balls havinga greater hardness than the sleeves. In the preferred form of theinvention an annular opening in the sleeve assembly for accommodatingeach ball is readily made by a single drilling operation. This drillingoperation produces radially aligned circular holes in the inner andouter sleeves having a diameter slightly larger than the diameter of theassociated ball. Since the elastomeric member is under compression thesize of the opening formed therein by the drilling operation is reducedwhen the drill bit is removed to a diameter slightly less than thediameter of the ball. Each ball is then inserted into a correspondingopening in the elastomeric sleeve with the elastic material yielding tosecurely hold the ball in an operating position out of contact with atleast one metal sleeve,

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but so that it can increasingly resist relative sleeve movement bycompression of the elastomeric sleeve. The ball can then makemetal-to-metal contact with diagonally opposed edges of the holes in theinner and outer sleeves to limit such movement in response to overloadof the elastomeric sleeve. The holes formed by the drilling operationeliminate the requirement for especially prepared drive contact surfacessuch as ball ramps frequently found in prior devices. Sufiicientclearance between the steel balls and the inner and outer sleeves isprovided to permit the elastomeric sleeve to damp substantially alltorsional vibrations in the drive line.

It is an object of this invention to provide an advancedtorque-transmitting coupling utilizing an elastomeric vibrationisolating and torque-transmitting device between drive and drivenmembers and featuring a rigid drive member supported by the elastomericdevice out of contact with the drive and driven members in normal torquetransmission and drivingly engageable with the drive and driven membersin response to torque overload of the elastomeric device to transmittorque therebetween, thereby preventing the slip of the elastomericdevice or the exceeding of the elastic limit thereof.

Another object of this invention is the provision of a yielding drivemember between drive and driven members to smother torsional vibrations,which yielding is limited by a new and improved rigid ball-stopconnection after predetermined shearing stresses have been imposed onthe yielding member to prevent slippage or further deformation thereof.

Another object of the invention is to provide a drive coupling havinginner and outer sleeves drivingly connected by an elastomeric memberunder compression between the sleeves and having circular radial holesformed therein for reception of spherical, rigid drive componentsnormally held out of driving contact with the sleeves but which respondto relative rotation of the drive and driven members to makemetal-to-metal contact with the inner and outer sleeves to limit furtherrelative rotation and transmit the drive.

Another object of this invention is to provide a new and improved methodfor making a flexible torque-transmitting coupling utilizing a ball-stopin a hole drilled into torque-transmitting and torque-receivingstructure.

These and other features and objects of the invention will become moreapparent from the following detailed descriptions and drawings in which:

FIG. 1 is a side elevational view partly in cross section showing adrive coupling in accordance with this invention between an input and anoutput member.

FIG. 2 is a view taken along lines 22 of FIG. 1.

FIG. 3 is a view of a portion of FIG. 2, illustrating operation of theinvention.

FIG. 4 is a hysteresis curve illustrating the vibrating dampingcharacteristics and the operation of this invention.

As shown in FIG. 1, there is a shaft 10, which for the purposes ofdescribing how this invention works, may be the crank shaft of aninternal combustion engine such as that shown in the US. Pat. 3,400,695issued Sept. 10, 1968 to K. Zaruba. This crank shaft drives a pulley 12,which in turn drives a belt 14 that is operatively connected to drive afan or other accessory, not shown. To transmit the drive from the shaft10 to the pulley 12 in this invention there is a drive couplingidentified generally at 15 which has a metallic inner cylindrical sleeve16 and a metallic outer cylindrical sleeve 18, drivingly connected by anelastomeric sleeve 20 compressed between sleeves 16 and 18. The drivecoupling 15 has a plurality of holes 22 therein, each formed by a singledrilling operation. Each hole is defined by an annular opening 22b and22a in the inner and outer metallic sleeves respectively and an annularopening 220 in the elastomeric sleeve. The openings 22a and 2212 areslightly larger in diameter than the diameter of a hardened steel ball24. Since the elastomeric sleeve is under compression, the diameter ofopening 220 will be slightly less than the diameter of the ball 24 whenthe drill bit is removed. This construction facilitates the assembly ofthe ball into openings 22 and provides for the retention of the ball inthe operating position by the elastomeric sleeve. As shown best in FIGS.1 and 2" the elastomeric sleeve tightly grips the ball 24 so that it canbe positioned at a station whereby the ball center is aligned with anaxis intermediate the internal and external diameter of the elastomericsleeve.

Since the diameter of the holes in the metallic sleeves is greater thanthat of ball 24, the ball is supported by the sleeve 20 out of contactwith the metallic sleeves. The ball has a diameter larger than thedifierence between the outer diameter of the inner sleeve and the innerdiameter of the outer sleeve or the radial thickness of the elastomericsleeve and has a diameter less than the difierence between the outerdiameter of the outer sleeve and the inner diameter of the inner sleeveor the radial thickness of the drive coupling. These constructiondimensions space the ball from contact with shaft so that the ball doesnot mechanically contact both pulley 12 and shaft 10 thereby keepingthese two components normally isolated by the elastomeric sleeve. Thesedimensions also permit the ball to provide a rigid driving connectionbetween the inner and outer sleeves when elastomeric sleeve isoverloaded.

As shown by FIG. 2, the distance between corresponding points ofdiagonally opposed contact surfaces 28 and or 32 and 34 at the peripheryof holes 22a and 22b is greater than the diameter of ball 24 when theelastomeric sleeve is not overloaded. However, under an overload in onedirection the elastomeric sleeve yields a suflicient amount so that thediagonal distance between 28 and 30 is sufliciently reduced to allow theball to drivingly contact these surfaces. In an overload condition in anopposite direction the contact surface 32 and 34 will make the drivingcontact.

As the ball moves from the FIG. 2 position to a driving position such asin FIG. 3 its engagement with edges 28 and 30 is effectively cushionedby the yieldable material 'whose rate of change of deflection decreaseswith increasing torque as the ball approaches driving contact to reduceshock of metal-to-rnetal ball engagement. This is illustrated best bythe hysteresis loop of FIG. 4 illustrating the vibration dampingcharacteristics of the invention. At 600 lbs. ft. clockwise torque forexample, on loading curve 0 of the loop, the deflection of theelastomeric sleeve rapidly decreases to cushion the subsequentengagement of the ball and the contact surfaces. The gradual change inslope of the curve near the stop points is in part, due to thecompression of the elastomeric sleeve by the ball. This increasedcompression of the elastomeric sleeve by the ball during relativemovement of the metal sleeves from the FIG. 2 position to the FIG. 3position is believed to be due to the fact that the perpendiculardistance or diameter of the hole in the elastomeric sleeve in thetransverse plane illustrated in FIGS. 2 and 3 and though the center ofthe ball decreases, this diameter is largest in the normal unstressedposition shown in FIG. 2 and decreases on increased relative movement tothe limit position shown in FIG. 3. Thus, with increasing torqueloading, the deflection first increases relatively rapidly, and thengradually without shock smoothly changes to a very slow rate of increaseof deflection with increasing torque loading as the stress in theelastomer changes from compression and shear to tension so the rate ofchange of deflection changes gradually and the coupling will sustain ahigher torque load without metal-to-metal contact than the elastomericsleeve alone and this will cushion the engagement of metal-to-metalcontact. Curve d illustrates the lag in the recovery of the elastomericsleeve on removal of the previously applied load. In the lower part ofthe loop, curve e represents a counterclockwise loading of the sametype, point t represents the engagement of the ball and the contactsurfaces, and curve represents the unloading of the sleeve.

The metal sleeves are slightly softer than the ball so that in initialuse, a seat is automatically formed on the ball contacting surface ofeach of the holes in the sleeves. In the illustrated embodiment of theinvention there are three balls in corresponding holes equally spaced inthe assembly as shown in FIG. 2. It will be understood, however, thatany suitable number of ball stops may be utilized as desired. In theassembly the balls are trapped in their associated holes by the pulleyand the shaft.

The elastomeric sleeve 20 will operate by torsionally flexing inresponse to occasional engine-excited torsional vibrations to dampvibrations and smooth the flow of power between the sleeve 10 and pulley12 and by flexing to compensate for overrun of the belt driven accessorysuch as the fan. In the event that there are overloads fromengine-excited torsional vibrations or other causes, the inner and outersleeves will rotate relative to one another causing the elastomericsleeve to flex and damp the vibrations. To prevent relative rotation orslippage between the elastomeric sleeve and the inner and outer steelannuli, the ball members will jam and make alternate metal-to-metaldriving contact at curved contacts 28 and 30 or 32 and 34 depending onthe direction of the overload. FIG. 3 shows surfaces 28 and 30 makingthe contact when the pulley load is excessive. This relative limitedangular travel of the inner and outer sleeve to a stop is preciselycontrolled thereby preventing the imposition of high shear stresses onthe elastomeric sleeve and prevents the exceeding of the elastic limitthereof. In a similar manner, the diagonally opposed curved contactsurfaces 32 and 34 will be effective to limit the deflection of theelastomeric sleeve or the relative slippage between the elastomericsleeve and the inner and outer annuli when the overload is in anopposite direction.

With this improved ball and radial hole construction, angular travel ofthe inner and outer sleeves relative to each other is precisely stoppedthereby adding to the effectiveness and efliciency and service life of aflexible coupling. The construction can be readily fabricated since onlydrilled radial openings and balls are employed and no special cammingsurfaces are needed.

It will be understood that this invention may be utilized in many otherenvironments for similar purposes. It may be used for example, intransmission controls, between the transmission control lever oractuator and the transmission. In such an environment the elastomericsleeve, having high internal friction, will dampen vibration andsuppress rattle which would otherwise be transmitted to the passengercompartment of a vehicle. A stabilized metal-to-metal drive between thelever and the transmission Would take place on gear change. Theinvention may also be effectively utilized in transmitting linearforces.

It will be appreciated that other modifications may be made to thisinvention in view of the teachings illustrated and described.

I claim:

1. In a drive transmitting coupling, an input member, an output memberfor driving a load, elastic means operatively connected between saidmembers for connecting said input member to said output member tothereby permit said input member to drive said output member,substantially rigid means supported by said elastic means, said inputand output members having diagonally opposed contact shoulders forcontacting said rigid means inresponse to overload of said output memberto permit said rigid means to transmit a driving force between saidinput and output members.

2. A coupling assembly for transmitting torque comprising an inputmember, an output member spaced from said input member, an elasticmember drivingly connecting said input and said output member, asubstantially rigid body carried by said elastic member and havingportions aligned with said input and said output members, said input andoutput members having contact surfaces normally spaced from saidsubstantially rigid body when said elastic member is transmitting torquebetween said input and output members and for drivingly contacting saidrigid 'body in response to a predetermined shear stress imposed on saidelastic member by said input and output member to inhibit said elasticmember from exceeding its elastic limit.

3. The coupling assembly of claim 2 wherein said input and outputmembers are sleeves, and said elastic member is an elastomeric sleevecompressed between said input member and said output member.

4. The coupling assembly of claim 2 wherein said input and outputmembers are inner and outer cylindrical metallic sleeves and saidelastic member is an elastromeric material compressed between saidsleeves, said substantially rigid member being a hardened steel ballsupported by said elastomeric material, and said contact surfaces beingformed by diagonally disposed curved walls of circular openings in saidsleeves which permit the insertion of said ball into said elastomericmaterial.

5. A torque transmitting coupling for drivingly connecting a rotatableinput member and an output member comprising an inner metallic sleevedrivingly connected to said input member and an elastomeric sleevemounted on said inner sleeve and an outer sleeve mounted on saidelastomeric sleeve and drivingly connected to said output member; saidsleeves being cylindrical and forming a yieldable drive between saidinput and said output members, an annular aperture in said couplingformed by annular openings in said sleeves, a spherical steel balldisposed in said elastomeric sleeve, said spherical steel ball having adiameter larger than the difference between the outer diameter of theinner sleeve and the inner diameter of the outer sleeve and having adiameter less than the difference between the outer diameter of theouter sleeve and the inner diameter of the inner sleeve, said openingsin said inner and outer sleeves being closed by said input and saidoutput members, said last mentioned openings forming curved anddiagonally disposed drive contact surfaces for solid driving engagementwith said ball in response to a predetermined torque applied to saidinput member subsequent to the angular deflection of said elastomericsleeve and a predetermined angular travel of said inner and said outersleeves relative to each other.

6. In a torque transmitting coupling an input member, an output member,yieldable means operatively connecting said members for dampingvibrations sustained by either of said members and for transmitting apredetermined torque load from either one of said members to the otherof said members, drive abutment means on each of said members, rigidmeans engageable with said drive abutment means but normally supportedby said yieldable means out of engagement with said drive abutment meanswhich effects deflection of said yielding means while transmittingtorque from one of said members to the other said member at a rate thatreduces as the torque load on said yielding means increases to cushionthe driving engagement of said rigid means with said drive abutmentmeans and to allow said yielding means to sustain its highest torqueload immediately prior to said driving engagement.

7. The torque transmitting coupling defined in claim 6 wherein saidmembers are inner and outer cylindrical sleeves and said yieldable meansis an elastomeric sleeve compressed between the inner and outer sleeves,said inner and outer sleeves and said elastomeric sleeve having anannular opening formed therein, said rigid means being a ball supportedin said hole in said elastomeric sleeve, said ball having a diametergreater than the radial thickness of the elastomeric sleeve and lessthan the radial thickness of said coupling formed by said sleeves.

8. The torque transmitting coupling defined in claim 6 wherein saidmembers are inner and outer cylindrical sleeves and said yieldable meansis an elastomeric sleeve compressed between the inner and outer sleevesto form a drive connection therebetween, said sleeves being formed witha plurality of annular openings formed therein, and said rigid meansbeing a spherical ball disposed in each of said openings.

9. In a power transmission having a rotatable input and an output, atorque transmitting coupling drivingly connecting said input and saidoutput, said coupling comprising an annular metallic sleeve mounted onsaid input for rotation therewith, an elastomeric sleeve mounted on saidmetallic sleeve and a second annular metallic sleeve mounted on saidelastomeric sleeve, said elastomeric sleeve being compressed betweensaid metallic sleeves to provide a yieldable drive connectiontherebetween, said coupling having at least one radial aperture formedtherein which is formed by aligned annular openings in said sleeves, ametallic ball having a diameter greater than the radial thickness ofsaid elastomeric sleeve and less than the radial thickness of said drivecoupling, said ball being supported in said-aperture in said couplingand in the opening in said elastomeric sleeve, said openings in saidmetallic sleeve having edge portions which face each other to providedrive contact surfaces spaced from said ball under a no load conditionon said coupling, said output being mounted on said outer metallicsleeve and over said aperture to confine said ball therein, said balland said contact surfaces providing a solid drive contact surfacebetween said metal sleeves in response to a predetermined torque loadapplied to said coupling to thereby prevent an overload being applied tosaid elastomeric sleeve.

References Cited UNITED STATES PATENTS 2,329,404 9/1943 Mace 6428 XR2,795,398 6/1957 Ragland 64-1l 2,955,443 10/1960 Fulop 6428 3,012,42112/1961 Cull 6411 3,252,301 5/ 1966 Herrington 6427 3,373,625 3/1968Keller 6427 XR JAMES A. WONG, Primary Examiner

